The present invention relates generally to heat removal systems and more particularly to heat removal systems for use with integrated circuits (ICs) and printed circuit boards.
As is known in the art, there is a trend to reduce the size of semiconductor devices, integrated circuits and microcircuit modules while at the same time having the devices, circuits and modules perform more functions. To achieve this size reduction and increased functionality, it is necessary to include a greater number of active circuits, such as transistors for example, in a given unit area. As a consequence of this increased functionality and dense packaging of active devices, such devices, circuits and modules (hereinafter collectively referred to as xe2x80x9ccircuitsxe2x80x9d) use increasingly more power. Such power is typically dissipated as heat generated by the circuits.
This increased heat generation coupled with the need for circuits to have increasingly smaller sizes has led to an increase in the amount of heat generated in a given unit area. To further exacerbate the problem, the circuits are often densely mounted on printed circuit boards.
This increase in the amount of heat generated in a given unit area has led to a demand to increase the rate at which heat is transferred away from the circuits in order to prevent the circuits from becoming damaged or destroyed due to exposure to excessive heat. To increase the amount of heat which such circuits can withstand, the circuits can include internal heat pathways which channel or otherwise direct heat away from the most heat-sensitive regions of the circuits.
Although this internal heat pathway technique increases the amount of heat which the circuits can withstand while still operating, one problem with this internal heat pathway technique is that the amount of heat generated by the circuits themselves often can exceed the amount of self-generated heat which the circuits can successfully expel as they are caused to operate at higher powers. Furthermore, other heat generating circuit components mounted on printed circuit boards proximate the circuits of interest further increase the difficulty with which heat can be removed from heat sensitive circuits. Thus, to increase the rate at which heat is transferred away from the circuits, a heatsink is typically attached to the circuits.
Such heatsinks typically include a base from which project fins or pins. The fins or pins are typically provided by metal extrusion, stamping or other mechanical manufacturing techniques. The heatsinks conduct and radiate heat away from the heat generating and thermally vulnerable regions of circuits. To further promote the heat removal process, fans are typically disposed adjacent the heatsink to blow or otherwise force air or gas through the sides of the fins or pins of the heatsink.
One problem with this approach, however, is that the amount of air or other gas which a fan or blower can force through the heatsink fins/pins is limited due to the significant blockage of gas flow pathways due to the fins/pins themselves. Furthermore, in a densely populated printed circuit board (PCB) or multi-circuit module (MCM), other circuit components and mechanical structures required to provide or mount the PCB or module present additional blockage to gas pathways and also limits the amount of gas flow through the heatsink thus limiting the effectiveness of the heatsink. Another approach has been to couple the fan directly on top of the heatsink, however the resulting assembly has significant height which makes this approach unusable in certain applications. Another approach has been to couple the fan directly on top of the heatsink, however the resulting heatsink and fan combination has significant height which makes this approach unusable in many applications.
The ability of such conventional heatsinks and heatsink fan assemblies is limited and is not sufficient to remove heat as rapidly as necessary to ensure reliable operation of state of the art devices, circuits and modules having increased thermal cooling requirements. It would, therefore, be desirable to provide a heat removal system which is capable of removing an amount of heat which is greater than the amount of heat removed by conventional heatsinks and to do so in a minimal amount of space and without significant expense. Additionally, it would be desirable to provide Electro-Magnetic Interference (EMI) protection in conjunction with the removal of heat from semiconductor devices, integrated circuits and microcircuit modules. Further it would be desirable to provide a heat removal system having a low profile.
In accordance with the present invention, a heat removal system comprises a gas supply such as a fan, a blower or a compressed gas source which is coupled to a first end of a duct. The second end of the duct is disposed about an axial fin heatsink. The duct includes a plurality of vanes disposed therein which enable the system to recover energy loss and provide more air through the system, which provides a concomitant increase in the cooling ability of the system. The vanes reduce turbulence and prevent boundary layer separation, thereby providing a maximum amount of gas flow to the heatsink. With this particular arrangement, a heat removal system which rapidly removes heat from devices, circuits and modules including high power CPU chips and custom ASICS is provided.